On Thu, May 21, 2020 at 10:05:17PM +0200, Thomas Gleixner wrote: > From: Thomas Gleixner <t...@linutronix.de> > > After a lengthy discussion [1] it turned out that RCU does not need a full > rcu_irq_enter/exit() when RCU is already watching. All it needs if > NOHZ_FULL is active is to check whether the tick needs to be restarted. > > This allows to avoid a separate variant for the pagefault handler which > cannot invoke rcu_irq_enter() on a kernel pagefault which might sleep. > > The cond_rcu argument is only temporary and will be removed once the > existing users of idtentry_enter/exit() have been cleaned up. After that > the code can be significantly simplified.
And yes, I see that the sole call to rcu_irq_enter_check_tick() does have instrumentation turned on, so good! ;-) Thanx, Paul